One of the funniest "most-embarrassing-moment" stories I've come upon in
a long time was about a lady who picked up several items at a discount
store.

When she finally got up to the checker, she learnt that one of her items
had no price tag.  Imagine her embarrassment when the checker got on the
intercom and boomed out for all the store to hear: "PRICE CHECK ON LANE
THIRTEEN, TAMPAX, SUPERSIZE."  That was bad enough, but somebody at the
rear of the  store apparently misunderstood the word "tampax" for
"THUMBTACKS."  In a business-like tone, a voice boomed back over the
intercom: "DO YOU WANT THE KIND YOU PUSH IN WITH YOUR THUMB OR THE KIND
YOU POUND IN WITH A HAMMER?"